The objective of the proposed investigation is to define the role of pili in the pathogenesis of infections in the genito-urinary tract. By using electronmicroscopic, tissue culture, and immunologic techniques we hope to determine the conditions under which attachment of piliated bacteria to epithelial cells occurs, if bacterial adherence is significant in vivo and whether protective specific immunity against pili develops in infected animals. It is hoped that these studies will shed light on host parasite interactions and help reduce morbidity and mortality or urinary tract infections.